Insulator



April 7, 1934- D. H. ROWLAND 1,955,609

INSULATOR Filed Aug. 4, 1930 Patented Apr. 17, 1934 UNITED STATES PATENTFFiCE INSULATOR Application August 4,

11 Claims.

' The invention relates to insulators and has for its general object theprovision of a radio-proof insulator in which there will be the effectof three or more condensers in series, one of which is of such lowcapacitance as to be capable of carrying most of the voltage undernormal line conditions.

A more specific object of the invention is to provide an insulator inwhich the construction is such that there will be the eflect of three ormore condensers in series, the inside one, preferably an air space,being of sufiiciently low capacitance to carry most of the voltage so asto relieve the elec tro-static stress on the tie wire connecting theconductor to the insulator, and the supporting pin for the insulator.

It is well known that the usual or common type of insulator comprisesone or more masses of dielectric material such as porcelain or the like.It is a common practice to provide an insulator of solid constructionmounted upon a metal pin and having a groove receiving and supporting aconductor which is held to the insulator by a tie wire engaging about aneck or within a groove on the insulator. It is with this usualarrangement in iew that I have devised my improvement which, morespecifically, comprises an insulator of porcelain or other similarmaterial formed as a hollow body with its lower end mounted upon asupporting pin and its upper end carrying the conductor and tie wire,there being, consequently, two layers of porcelain and a layer of airbetween the conductor and the support so that in accordance withaccepted theories there will be the effect of a plurality of condensersin series between the con- 35 ductor and the grounded support.

Another important object of the invention is to provide an insulator ofthis type which may be formed in sections which may be cast or plungedand which are subsequently united so as to form, in effect, ahomogeneous whole as the parts are subsequently indivisible orinseparable.

Another object of the invention is the provision of an insulator havingthe above mentioned characteristics and which, in addition, is so shapedas to offer the minimum resistance to air currents, thereby making itfree from accumulations of dirt and other undesirable foreign matterupon it which might influence its resistance to leakage currents, theshape being moreover such that rain water impinging upon the insulatorwill wash the surfaces clean even under the most adverse conditions asfor example if the insulator be used near cement works and other placeswhere there is a large amount of foreign matter floating in the Cir1930, Serial No. 472,914

An additional object is to provide an insulator having these advantagesand which will at the same time be simple and inexpensive to make, justas easy to install as any other, positive in action, efiicient anddurable in service, and a general improvement in the art.

To the attainment of the foregoing and other objects and advantageswhich will appear as the description progresses, my invention preferablyconsists in the details of construction and shapes of surfaces to behereinafter more fully described and claimed, and illustrated in theaccompanying drawing in which:

The figure is a view of an insulator constructed in accordance with myinvention, one half being in elevation and the other half in section.

Referring more particularly to the drawing I have shown the insulator ascomprising a hollow porcelain body including a lower section 10 and anupper section 11, both concave-convex in cross section and arranged withtheir open sides toward each other. As all the external and internalsurfaces are surfaces of revolution it is quite apparcut that thesesections may be readily formed by plunging in the usual and well knownmanner though it is of course conceivable that they may be cast if suchis preferred for any reason. The lower section 10 is arranged with itsconvex side down and this convex surface may be either a portion of asphere or of compound curved shape, as preferred. The lower section isalso formed at its center with an upstanding projection 12 formed with arecess or socket 13 which may be sanded or otherwise roughened inaccordance with common practice and which is intended to receive asuitable pin, not shown, which is cemented into the recess and which isfor the purpose of supporting the insulator upon a cross arm or otherequivalent support.

The upper section 11 has its convex side disposed upwardly and it is ofgreater diameter than the lower section so as to extend beyond theperiphery thereof for the purpose of shedding rain or in fact anyaccumulation of moisture. Spaced inwardly from its edge the uppersection is formed with a ledge or shoulder 14 closely abutting upon thecorresponding upper edge of the lower section 10. At its center theupper section is formed with a head 15 joined thereto by a constrictedneck 16 which provides or defines a groove 17 for the reception of theconventional or any preferred tie wire, clamp or the like for holdingthe conductor, not shown, in the conductor receiving slot 18 at the topof the head 15.

In the manufacture and assembly of an insulator of this type it shouldbe understood that after the sections 10 and 11 have been preformedeither by plunging or casting, or any other method, the sections arearranged in superposed relation as shown with the ledge 14 engagingsnugly upon the edge of the lower section. It is intended that slip orglaze be provided on these contacting surfaces. If the sections are tobe assembled while in a green or slightly plastic condition then it isprobable that clay slip would be used at the areas of contact betweenthe two sections but if assembly is contemplated while the sections arein a bone dry condition, which may conceivably be preferable, then glazewould be the medium applied to the contacting surfaces for the purposeof uniting them. In any event, after the sections are assembled they arefired in a kiln in the usual manner and owing to the fact that theassembled sections are hollow it is necessary to permit the escape ofair from the interior during firing. This is readily taken care of byproviding the lower section with a series of small holes 19 whichincline downwardly and outwardly as clearly indicated in the drawing sothat water cannot enter the interior even though gusty rains may beatupon the insulator. Of course it is also obvious that all the exteriorsurfaces of the sections are glazed in the usual manner before firing.

After assembling and firing, it may be well to pour in a filler 20 ofmelted asphaltum or the like in the groove between the outer edge of thelower section and the inner surface of the overhanging outer portion 21of the upper section, the purpose of this being to seal and additionallysecure the sections especially in case there might be any slight lack ofcohesion between the contacting surfaces. Moreover this filling willpreclude any accumulation of moisture or dirt at the joint.

In use, the insulator is mounted upon a pin which is cemented within therecess 13, the conductor is laid in the groove 18 and whatever tie wireis used is engaged with the conductor and disposed within the groove 17.

Attention is directed to the fact that in this insulator there will bethe efiect of a series of condensers between the conductor and thesupporting hardware as each thickness of porcelain with its outer andinner surfaces acts as one condenser and as the interposed air togetherwith the inner surfaces of the sections will act as another. A veryimportant feature is the air space which is directly interposed betweenthe conductor and the pin and which greatly increases the insulatingvalue or puncture strength. The fact that the dielectric constant orpermitivity of air is only one-sixth that of porcelain causes thecapacitance of the condenser formed by the air space to be very muchlower than that formed by the two porcelain parts since the capacitanceis indirectly proportional to the permitivity. As the air is notentirely confined, owing to the provision of the holes 19, there will beno great ionization, at least not sufficient to impair the electricalefiiciency. An insulator constructed in this way is particularlyadvantageous for use as it may be said to be radio-proof, that is to sayit will cause no great disturbances such as occur with the ordinarytypes embodying one or more sections of solid porcelain without anyinterposed air gap. Another feature of importance is the stream-lineshape of the insulator which will insure the surfaces being wetted whenrains occur so that there will be no unequal electrical stresses set upand so that the surfaces will be adequately washed off so as to preventthe accumulation of dirt and foreign matter which, in some localities inparticular, is highly conductive and leads to excessive leakage over thesurface.

From the foregoing description and a study of the drawing it is thoughtthat the construction, operation and advantages will be readily apparentto one skilled in the art without further explanation.

While I have shown and described the preferred embodiment of theinvention, it should be understood that the disclosure is merely anexemplification of the principles involved as the right is reserved tomake all such changes in the details of construction as will widen thefield of utility and increase the adaptability of the device providedsuch changes constitute no departure from the spirit of the invention orthe scope of the claims hereunto appended.

Having thus described the invention, I claim:

1. An insulator comprising a dielectric body including upper and lowersections concave-com vex in cross section arranged with their concavesides toward each other to define an interposed air space, one sectionbeing formed for mounting upon a support and the other for attachment toa conductor, the upper section extending outwardly beyond the lowersection.

2. An insulator comprising a dielectric body including upper and lowersections concavo-convex in cross section arranged with their concavesides toward each other to define an interposed air space, one sectionbeing formed for mounting upon a support and the other for attachment toa conductor, the upper section projecting outwardly and downwardlybeyond the upper edge of the lower section, and sealing means about theupper edge of the lower section.

3. An insulator comprising a dielectric body including upper and lowersections concavo-convex in cross section arranged with their concavesides toward each other to definite an interposed air space, one sectionbeing formed for mounting upon a support and the other for attachment toa conductor, the upper section having a downwardly and outwardlyextending skirt portion projecting beyond the upper edge of the lowersection, the inner surface of said skirt portion defining, with theupper edge of the lower section, a groove, and sealing material withinsaid groove.

4. An insulator comprising a pair of sections concavo-convex in crosssection arranged with their concave sides toward each other to define aninterposed air space, the upper section being formed inwardly of itsperiphery with a ledge seating conformingly upon the upper edge of thelower section, and being formed for engagement with a conductor and theother having a i refiexly curved portion defining a socket for mountingupon a support.

5. An insulator comprising a pair of sections concavo-convex in crosssection arranged with their concave sides toward each other to define aninterposed air space, the upper section being formed inwardly of itsperiphery with a ledge seating conformingly upon the upper edge of thelower section and united thereto whereby both N sections will constitutea homogeneous whole.

6. An insulator comprising a pair of sections seating conformingly uponthe upper edge of the lower section and united thereto whereby bothsections will constitute a homogeneous whole, one section having meanspermitting communication between the interior and the atmosphere.

7. An insulator comprising a pair of sections concavo-convex in crosssection and arranged with their concave sides toward each other with theperiphery of one section extending outwardly beyond that of the other toform a water drip, said sections being secured together at the edge ofone.

8. An insulator comprising a pair of sections concave-convex in crosssection and arranged with their concave sides toward each other with theperiphery of one section extending outwardly beyond that of the other toform a water drip, said sections being secured together at the edge ofone, one section having an inwardly extending projection with a recesstherein for engagement upon a supporting pin and the other having atransversely grooved conductor supporting head joined thereto by aconstricted neck.

9. An insulator comprising upper and lower sections concavo-convex incross section arranged with their concave sides toward each other todefine an included air space, the upper section being of greaterdiameter than the lower to project outwardly beyond the same and beingformed with a ledge united to the edge of the lower section, the lowersection having means for engagement upon a support and the upper sectionhaving means for supporting a conductor.

10. An insulator comprising upper and lower sections concavo-convex incross section arranged with their concave sides toward each other todefine an included air space, the upper section being of greaterdiameter than the lower to pro- J'ect outwardly beyond the same andbeing formed with a ledge united to the edge of the lower section, thelower section having means for engagement upon a support and the uppersection having means for supporting a conductor, the lower sectionfurther having a circumferential series of holes therein establishingcommunication between the air space and the atmosphere.

11. An insulator comprising upper and lower sections concavo-convex incross section arranged with their concave sides toward each other todefine an included air space, the upper section being of greaterdiameter than the lower to project outwardly beyond the same and beingformed with a ledge united to the edge of the lower section, the lowersection having means for engagement upon a support and the upper sectionhaving means for supporting a conductor, the lower section furtherhaving a circumferential series of holes therein establishingcommunication between the air space and the atmosphere, said holes beinginclined upwardly toward the axis of the insulator to prevent entranceof water.

DAVIDGE H. ROWLAND.

